In an electrostatic imaging process, a copy of an original image is produced by forming a toner image from a latent electrostatic image, which is then transferred to a target substrate, such as paper. The latent electrostatic image is generated by initially charging a photoconductor to create a uniform electrostatic charge of a particular polarity over the surface of the photoconductor. As an example, the photoconductor can be charged by exposing the surface of the photoconductor to a charge corona. The uniformly charged surface of the photoconductor is then patterned by selectively directing a modulated beam of light, such as a beam of laser light, to form the latent electrostatic image. Using charged toner particles having opposite polarity of the photoconductor surface, the latent electrostatic image is developed into the toner image by applying the charged toner particles to the photoconductor surface, which selectively adhere to the photoconductor surface according to the latent electrostatic image.
There are two distinct types of electrostatic imaging machines. The first type of electrostatic imaging machines uses dry toner to form toner images. The second type of electrostatic imaging machines uses liquid toner to form the toner images. Liquid toner generally includes toner particles and charge director compounds that are dispersed in a dielectric hydrocarbon-based carrier liquid, such as hydrocarbon solvents sold under the name of ISOPAR, which is a trademark of the Exxon Corporation. In some electrostatic imaging machines, the liquid toner is formed within the machine by mixing concentrated toner solvent, charge director compounds and dielectric hydrocarbon-based carrier liquid. In these electrostatic imaging machines, after the liquid toner is used, the used carrier liquid is extracted from remaining liquid toner by evaporating the carrier liquid and then condensing the evaporated carrier liquid. The used carrier liquid is then collected in a receptacle. The used carrier liquid cannot be reused in an electrostatic imaging process, so the carrier liquid is discarded. When additional carrier liquid is needed, new carrier liquid is introduced to the machine to produce more liquid toner.
A concern with the above-described electrostatic imaging machines is that the machines continuously use carrier liquid, and consequently, continuously produce used carrier liquid. Used carrier liquid, such as ISOPAR, is hazardous waste and must be disposed in a proper manner. The disposal of used carrier liquid adds significant cost and time to the operation of the electrostatic imaging machines. Furthermore, since the used carrier liquid is treated as hazardous waste, the operation of the electrostatic imaging machines contributes to the environmental problem of hazardous waste disposal.
In view of these concerns, there is a need for a system and method to reduce or eliminate hazardous waste in the form of used carrier liquid produced by electrostatic imaging machines and to reduce operator interventions.